Numerous methods are known in the prior art for applying a coating to a substrate, including dip coating, spray coating, spin coating, screen printing and tape casting. Each of these methods may result in a uniform coating thickness depending on the shape of the substrate and the type of coating material applied. In some instances these methods are not useful with various types of coating materials; for example, the desired coating thickness cannot be achieved or cannot be achieved with the desired uniformity. Similarly, the shape of a particular substrate may create coating problems when one of the above methods is used.
In order to overcome some of the problems with non-uniform thickness of coating, doctor blades have been used, where the blade is moved past the substrate or the substrate is moved past the blade after coating material has been applied to the substrate. The movement of the doctor blade with respect to the substrate creates a uniform thickness of coating material on the substrate. Heretofore doctor blades have been flat, like the edge of a razor blade and are therefore limited in usefulness to substrates having flat surfaces. In addition, the doctor blade and substrate are generally moved linearly with respect to each other. Linear movement, however, is not suitable for the shapes of many types of substrates, especially those substrates with curved surfaces. Thus, a device and method for uniformly coating devices having curved surfaces, such as rods or toroids, is still needed.